It is a concept that forms a cornerstone of our understanding of the universe and the concept of time -- nothing can travel faster than the speed of light.

But now it seems that researchers working in one of the world's largest physics laboratories, under a mountain in central Italy, have recorded particles travelling at a speed that is supposedly forbidden by Einstein's theory of special relativity.

Scientists at the Gran Sasso facility will unveil evidence on Friday that raises the troubling possibility of a way to send information back in time, blurring the line between past and present and wreaking havoc with the fundamental principle of cause and effect.

They will announce the result at a special seminar at Cern -- the European particle physics laboratory -- timed to coincide with the publication of a research paper describing the experiment.